OCR A2 F325: Equilibria, Energetics and Elements, 17 June 2014Watch
While you're waiting for an answer, did you know we have 300,000 study resources that could answer your question in TSR's Learn together section?
We have everything from Teacher Marked Essays to Mindmaps and Quizzes to help you with your work. Take a look around.
If you're stuck on how to get started, try creating some resources. It's free to do and can help breakdown tough topics into manageable chunks. Get creating now.
Not sure what all of this is about? Head here to find out more.
Hey Guys, hows revision coming along? Can anyone explain how you draw those titration curves, and how you decide on using a suitable indicator and so on? Im so confused, I can work out the pH of the acid and alkali but how do you work out the equivalence point and the volume? Its so confusing, any help would be great, thanks
strong acid vs strong alkali
strong acid vs weak alkali
weak acid vs strong alkali
weak acid vs weak alkali
now for the first example you have a strong acid, so a good example would be HCl (strong acids will have pH close to 1) and a strong alkali such as NaOH (strong alkali would level off at a pH of about 13.5)
so when you actually draw this on a graph it would have a line coming out of pH at around 1 and slowly rising, and when reached at 25cm3 there will be a dramatic increase in pH, this is called the end-point its where there is a colour change. what happens is that you have a solution of HCl and you titrate it by adding NaOH, when most all all HCl have reacted there will be a colour change.
because this is a strong alkali the graph would level off at pH of around 13.5
the equivalence point is when H+ = OH- t
by using certain indicators we are able to figure out the pH, in the exams they give you 3 examples of indicators with pH range and ask you to conclude which indicator will be used, and by looking at the around the equivalence point you are able to see which indicator you will use...
let me explain:
strong acid vs strong alkali will give you a pH of 7 (the equivalence point)
what i do to help me out is mark a line at the start of the increase.. so at 25cm3 there will be an increase and at the start of that increase i will put a mark, next i will put a mark just about where it levels off, and then from those 2 i will add a middle line, and try to get a reading from that, but the best way of learning it, is by understanding the pH levels you will get for the different types of titration curves.
well i hope i helped, all the other types follow the same rule but the shapes would be different and i believe you have examples in your book or so, if you don't let me know and i will try to explain to you.
if i missed anything out let me know